Blockwise Fragile Watermarking Schemes for Tamper Localization in Digital Images

This paper presents two fragile watermarking schemes for tamper localization in digital images. In the first scheme, the unprotected image is divided into 8×8 blocks. A 128 bit hash value is computed for each block by using MD5 algorithm. They are embedded into the two LSBs of the pixel value. The same pattern is used in the second scheme with slight modifications; the block size is 16×16, SHA-256 algorithm is used to generate a 256 bit hash value and they are inserted into the LSB of the pixel value. Experimental results show that the schemes can resist collage, vector quantization, content only and constant average attacks. The schemes provide better tamper detection rate.